Preparation of hard dental tissues for a metal-ceramic crown. Stages of preparation of a mandibular molar for a full cast crown. Grinding of teeth for solid metal crowns.

Preparation of a tooth or grinding of a tooth for further installation of a metal-ceramic crown on it means cutting down special hard shells of the tooth, represented by mineralized tissues - dentin and enamel.

Why is this technique needed?

Specific grinding of teeth for metal-ceramic dentures has features that are unique to this method.

Before installing a new prosthesis, it is necessary to cut down some of the mineralized tooth tissue. In order to carry out this work, it is necessary to numb the area where these procedures will be performed as much as possible. Teeth with complex banded pulp are especially in need of anesthesia.

In order to numb the desired area, modern dentistry uses several methods of anesthesia, as well as some types of anesthetics. The method of anesthesia that is carried out along the nerve trunk, as well as by injecting an anesthetic with a special needle into the mucous parts of the gums, is very popular.

These types of anesthesia require close attention from a specialist, as well as strict adherence to all necessary precautions. This is necessary in order not to infect the patient, as well as to prevent infection with various types of viral infections transmitted through blood - hepatitis viruses or immunodeficiency viruses.

When carrying out pain relief measures, several types of solutions are used:

• "Lidocaine";
• "Xylocytin";
• "Artikain";
• "Ubistezin";
• "Ultracaine".

"Lidocaine" solution

The most effective among the above-mentioned medicinal anesthetics is Ultracaine. This drug perfectly freezes the part of the gum that needs to be treated and keeps it frozen for a long time.

It also happens that the patient feels anxious and cannot pull himself together before the procedures. For this purpose, premedication is provided, which consists of administering small doses of tranquilizers to the patient to relieve anxiety symptoms. Premedication is given 30-45 minutes before anesthesia.

For premedication, some drugs from the following list are given:

• "Phenibut";
• "Mebicar";
• "Tazepam";
• "Elenium";
• "Diazepam."

"Elenium"

In modern techniques, in order to significantly increase the effect of anesthetics, the addition of vasoconstrictor drugs is used. These substances are capable of spasmodic vessels along the bloodstream, which are located in the periphery. This leads to local oxygen starvation in the tissues at the injection site. This reduces the excitability and conductivity of nerve fibers.

It has been proven that the use of vasoconstrictors in modern methods of dental procedures leads to a decrease in the effect of toxic substances contained in the anesthetic. And the painkiller itself is required several times less.

Vasoconstrictor drugs used in dental practice are:

• a hormone produced by the adrenal cortex - adrenaline;
• a hormone produced by the pituitary gland - vasopressin.

It also happens that total general anesthesia is necessary. This technique is used quite rarely and is necessary for the following indications:

• patient intolerance to local anesthesia or complete lack of pain relief effect;
• diseases associated with the nervous system, leading to convulsive contractions (chorea, hyperkinesis).

To use general anesthesia, the drug “Rotilan” is used; it has a fairly pronounced, but at the same time mild effect. It is also important that the specialist does not lose contact with the patient.

In order to avoid touching soft tissue when grinding hard parts of a tooth, the specialist must know well what depth is maximum for a certain part of each tooth.

Features of turning

When carrying out manipulation, you need to remember some features. The main feature is the creation of a special ledge - circular or vestibular. This ledge is necessary in order to subsequently create the edge of the crown part, which is necessary for veneering the ceramic part of the crown. In addition, thanks to the pre-created ledge, the edge of the installed and fixed crown will not injure or injure part of the soft tissue of the gums with which it will come into contact.

Video - Turning with a ledge

Further manipulation and creation of a special ledge depend on the facts of clinical manifestations, such as:

• the degree of destruction of the desired tooth;
• placement of the tooth cavity;
• height of the created metal-ceramic crown;
• patient's age.

The use of special attachments allows you to control the thickness of the edge of mineralized tissue being ground. Using these attachments, you can create special marking grooves, which will later serve as a guide for the specialist. The bottom of the groove should be at the same level as the edge of the gum, this will mean that the necessary part of the tooth has already been cut down, and further manipulations can begin.

Teeth must be prepared for further installation of metal-ceramic crowns. This is done with specialized diamond-coated or carborundum-coated nozzles. These types of nozzles can be in the shape of a needle or a flame.

Strong discrepancies in the surfaces that should be in contact make it impossible to install a metal-ceramic crown. Otherwise, a strong touch worsens the process of fixing the crown, which can further lead to injury to the loose and fibrous building tissue of the tooth.

After removing unnecessary tissue between the teeth, several thin, special attachments, cylindrical or cone-shaped, are used and the entire surface that will be in contact is treated. Next, a special ledge will be formed.

Before proceeding with the formation of the necessary ledge, the specialist must decide which one will be suitable in this case. There are several varieties, namely:

• a rounded ledge with a groove is the most commonly used option. Most specialists use this option for creating a ledge before installing a metal-ceramic structure. The width of such a ledge ranges from 0.7 to 1.3 mm, which will subsequently preserve the hard tissues of the tooth - enamel and dentin;
• A ledge made in the form of a knife is a good option when installing solid crowns, as well as teeth that have slopes. The width of such a ledge is narrower than rounded. It ranges from 0.4 to 0.5 mm;
• the shoulder type of ledge is the least effective, but the most aesthetic type. It reaches 2 mm in width.

Video - Tooth preparation for a crown

The need to create a ledge

Specialists do not always make a ledge when grinding a tooth before placing metal-ceramic crowns. There are several reasons for this:

1. The turning time, which is done without a special ledge, is reduced several times.
2. When creating the necessary ledge, you need to have a specialized set of materials and tools, as well as experience working with them.
3. In order to prepare a tooth and create the desired ledge, it is necessary to have a specialized thread that is laid in the space between the gums and teeth. This technique is necessary in order to protect the gums when working with special attachments and creating the necessary ledge. To place this thread you need a specialized tool.
4. Availability of expensive material from which the impression will be made.
5. A mass is needed from which the so-called “shoulder” will be formed in the future.

It is worth noting that a tooth prepared without a ledge can become infected, and the tooth itself can be destroyed. This can cause inflammation of the gums and many complications in the future.

Below are popular methods for grinding teeth for metal-ceramic crowns.

It often happens that after installing metal-ceramic crowns, the patient experiences discomfort and pain in the area of ​​the new prosthesis. The reasons for this may be:

• violation of the procedure for grinding mineralized tissue.
• inflammation of the apical part of the tooth and processes of inflammatory etiology in the soft tissues of the tooth.

In all possible pathological conditions, it is necessary to contact a specialist as soon as possible to correct these errors. Otherwise, complications may develop.

Video - Preparing teeth. Dental prosthetics with a crown

Preparation, or grinding, is a procedure in which a certain amount of tooth tissue is removed to change its size and/or shape. Why is this procedure performed and how is preparation for a metal-ceramic crown done?

Why is turning done?

The main goal of preparation is to create conditions for the crown to be securely fixed and not create inconvenience for the patient. Important features of this process:

• It is one of the main stages of prosthetics, which largely determines the quality of the doctor’s work.
• It is irreversible. It is no longer possible to return a tooth to its original shape after grinding, so it is very important that the procedure is performed correctly.

This manipulation has several goals:

1. Creating a tooth shape that allows the crown to be securely fixed to it.
2. Organization of additional space for securing an artificial structure.
3. Ensuring a tight, but at the same time non-traumatic fit of the edge of the crown to the edge of the gum.

consists of a metal base and a ceramic coating. Thanks to this device, it is reliable and aesthetically pleasing, but at the same time it requires sanding a fairly large amount of tissue.

Grinding is necessary for a tight fit of the crown to the tooth.

Ledges

Preparing teeth for installation of a metal-ceramic structure involves the use of one of two technologies.

1. No ledge. At the same time, the tooth is ground down, an impression is taken, from which a prosthesis is prepared in the laboratory. Once installed, it will sink under the gum so that the edge of the crown is invisible.

The edge thickness is at least 0.8 mm, since it is technologically impossible to make it thinner (both metal and ceramics end at the same level). There is a lot of pressure on the gums, which can result in periodontitis, gingivitis and other diseases. As a result, they will lead to receding gums and exposure of the metal edge.

1. With a ledge- the only correct method in modern conditions. He assumes that during the processing of the tooth a small step about 1 mm wide is made, on which the edge of the prosthesis will be located. As a result, overhanging edges and excessive pressure on the gums are eliminated.

Ledges vary, and the choice of treatment plan is determined based on individual characteristics, which are revealed during visual examination and x-rays.

• A ledge-shoulder covered by both the metal base of the crown and ceramics.
• A ledge-shoulder with a bevel, as well as a rounded ledge with a bevel, covered only by metal.

Turning with a shoulder is not done in all clinics, since this prolongs the production time of the prosthesis and requires additional skills from the dental technician and orthopedist. However, it is better to give preference to institutions that practice this technique, since it reduces the risks of complications several times.

Features of preparation for metal ceramics

Before installing metal ceramics, a significant amount of tissue is removed.

Working with metal-ceramics has a number of features:

• Since the volume of tissue removed is significant, tooth preparation for a metal-ceramic crown is always carried out under local anesthesia.
• Most often, the pulp is removed because it can be damaged when working with hard tissue. There are so-called safety zones, the size of which depends on the age of the patient and the type of tooth on which the prosthesis will be installed. But doctors in many clinics prefer not to take risks and carry out the procedure in advance.
• The stump should have a slightly conical shape (with an angle of 3 to 20 degrees). This is necessary to ensure that there is no tension in both the frame and the cladding.

The algorithm used to prepare teeth for a metal-ceramic crown is somewhat different from turning for structures made of other materials:

1. Grooves are made on the vestibular surface with a diamond bur.
2. Hard tissues are ground down to the level of the bottom of the grooves.
3. Diamond discs are used to remove tissue from the distal surfaces.
4. Using the depth of the grooves as a guide, tissue is removed from the labial and oral surfaces, creating a ledge at the level of the gingival margin.
5. The chewing surface and cutting edge are prepared.

Tooth processing requires compliance with certain rules:

• Brief touch with the bur, no longer than 2-3 seconds at a time.
• Throughout the entire operation, the tool is cooled using an air-droplet jet.
• Tools must have a high abrasive speed and be well centered.

Compliance with these requirements will allow you to avoid injuries, the most common of which are soft tissue injury, excessive grinding, and damage to adjacent teeth.

The ledge reduces the risk of complications.

The thickness of the metal-ceramic single prosthesis is about 1.5-1.7 mm. Consequently, the fabrics should be reduced by exactly this amount on all sides.

Working with metal-ceramics has other peculiarities:

• • Since the volume of tissue removed is significant, tooth preparation for metal ceramics is always carried out under local anesthesia.
  • Most often, because it can be damaged when working with hard tissues. There are so-called safety zones, the size of which depends on the age of the patient and the type of tooth on which the prosthesis will be installed. But doctors in many clinics prefer not to take risks and carry out pulp removal in advance.
  • In order to avoid complications and extend the service life of the structure, the formation of a ledge, as discussed above, is required.

Ideally, many of the patient's problems are resolved with the installation of a crown. However, it also happens that after this procedure additional troubles begin. To prevent this from happening, you should carefully choose the clinic where the prosthetics will be performed.

Sources:

1. Ryakhovsky A.N., Ukhanov M.M., Karapetyan A.A., Aleynikov K.V. Review of methods for preparing teeth for metal-ceramic crowns. // Panorama of orthopedic dentistry, No. 4, 2008.
2. Orthopedic treatment using metal-ceramic dentures. Ed. V.N. Trezubova. Moscow, 2007.

Porcelain crowns

Plastic crowns

Stamped metal crown

Solid metal crown

Solid metal crown with veneer

Tver State Medical Academy

Department of Orthopedic Dentistry with courses in implantology and aesthetic dentistry

Head of the department - Honored Scientist of Russia,

Doctor of Medical Sciences Professor A.S. Shcherbakov

Cast all-metal and combined crowns (metal-plastic, metal-ceramic). Conditions and indications for prosthetics. Principles and methods of tooth preparation. Double (corrected) impression with retraction of the gingival margin.

(guidelines for students)

Compiled by Ph.D., Associate Professor I.V. Petrikas

Lesson topic:“Cast all-metal and combined crowns (metal-plastic, metal-ceramic). Conditions and indications for prosthetics. Principles and methods of tooth preparation. Double (corrected) impression with retraction of the gingival margin.”

Purpose of the lesson: study the conditions and indications for prosthetics with cast all-metal and combined crowns; learn to take double impressions with silicone impression compounds, master the technique of retraction of the gingival margin.

Key words and designations:

HF – upper jaw,

LF – lower jaw,

Rg – x-ray,

Mate – cast, combined crown,

STK – light-hardening composite material,

Background knowledge.

Combined crowns- these are metal crowns that have a plastic lining on the vestibular surface, or a plastic, composite or ceramic coating on all sides.

1. The types of combined crowns are presented in Table 1.

Table 1

Types of combined crowns

2. Silicone impression materials.

2.1. Two types of silicone impression materials (C-silicones and A-silicones),

2.2. Viscosity grades of silicone impression materials,

2.3. Positive properties and negative qualities of silicone impression materials.

3. Methods for retraction of the gingival margin.

3.1. Mechanical method of retraction of the gingival margin (indications and materials),

3.2. Mechano-chemical methods of retraction of the gingival margin,

3.3. Chemical methods of retraction of the gingival margin.

TASKS TO CONTROL THE INITIAL LEVEL OF KNOWLEDGE.

1. SILICONE AND THIOCOL IMPRESSION MATERIALS USED

FUCKING FOR

duplication of models,

obtaining double (corrected) impressions,

obtaining functional impressions from toothless jaws,

obtaining functional impressions with partial loss of teeth,

volumetric modeling of the polished surface of a complete denture.

obtaining an impression when relining the prosthesis,

obtaining an impression using a copper ring.

2. THE BASIS OF SILICONE IMPRESSION MATERIALS IS

sodium salt of alginic acid,

eugenol, talc, zinc oxide,

beeswax, paraffin, rosin,

silicon-organic polymers.

SILICONE AND THIOCOL IMPRESSION MATERIALS OF LOW VISCOSITY ARE USED AS

the first, main layer in double prints,

second, corrective layer in double prints.

SILICONE IMPRESSION MATERIALS INCLUDE

1) Sielast (Ukraine), 5) Stomaflex (Czech Republic),

2) Vigalen (Russia), 6) Exaflex (Japan),

3) Elastic (Czech Republic), 7) Stomalgin (Ukraine),

4)President (Switzerland), 8) 1+2+3+5+7,

POLYSULFIDE (THIOCOL) AND SILICONE IMPRESSION MATERIALS ARE ARTIFICIAL_____________________ COLD VULCANIZATION.

To retract the gingival margin in a 20-year-old patient, you will use:

retraction threads,

retractors and mechanical rings,

retraction gel

To retract the gingival margin in a 60-year-old patient with moderate periodontitis and cardiovascular pathology, you will use:

1) threads impregnated with retraction liquids,

2) retractors and mechanical rings,

3) retraction gels and pastes with adrenaline-containing substances

End of table 14

Test tasks to control the assimilation of material

1). Shape of a tooth prepared for a solid crown:

a) truncated cone

b) reverse cone

c) cylindrical

d) arbitrary

2). The taper of the tooth stump prepared for a solid-cast crown is (degrees):

3). Preparation for a solid crown:

a) necessarily with the formation of a ledge

b) without forming a ledge

c) possible both with and without the formation of a ledge

d) carried out with the formation of a circular groove

4). When preparing for a cast crown without a shoulder, the vestibulo-oral surfaces of the tooth are ground off:

a) by 0.25-0.3 mm

b) by 0.1-0.2 mm

c) to the level of the cervix

d) to the level of the gums

d) below the level of the cervix

5). Treatment of the chewing surface of a tooth when preparing for a cast crown is usually carried out:

a) carborundum disc

b) needle-shaped diamond bur

d) diamond-shaped diamond bur

e) ellipsoidal diamond bur

6). When preparing the occlusal surface for a solid-cast crown, hard tissues are ground to a thickness (mm):

7). Treatment of the contact surfaces of the tooth when preparing for a cast crown is carried out:

a) carborundum disc

b) cone-shaped diamond bur

c) double-sided diamond disc

d) elliptical diamond bur

8). Pre-treatment of the vestibulo-oral surfaces of the tooth when preparing for a cast crown is carried out:

a) carborundum disc

b) needle-shaped diamond bur

c) double-sided diamond disc

d) large cylindrical diamond bur

e) reverse cone diamond bur

9). When preparing for a cast crown, the palatal surface of the incisors and canines is ground off:

a) by 0.25-0.3 mm

b) by 0.1-0.25 mm

c) by 0.3-0.5 mm

d) by 0.35-0.4 mm

e) by 1.5-2.0 mm

10). Angle of convergence of the lateral walls of the tooth prepared for a cast crown (in degrees):

Mandatory:

1. Trezubov V.N., Shcherbakov A.S., Mishnev L.M. “Orthopedic dentistry. Propaedeutics and the basics of a private course." Medpress, 2011.416 p.

2. Orthopedic dentistry. Textbook / Ed. N.G. Abolmasova.- M.: Medpress-inform, 2009.- UMO. 504 s

Additional:

1. Zhulev E.N. "Fixed dentures." Publishing house MIA, 2010. 488 p.

2. Konovalov A.P., Kuryakina N.V., Mitin N.E. “Phantom course of orthopedic dentistry” / ed. Trezubova V.N. – M.: Medical book; N. Novgorod: Publishing house NGMA, 2003. 341 p.

PRACTICAL LESSON No. 6

Subject: Tooth preparation for cast and veneered (combined) and plastic crowns. Types of ledges, their shapes, location, creation methods. Requirements for a correctly prepared tooth in the manufacture of combined and plastic crowns. Clinical and laboratory stages of crown manufacturing.

Motivational characteristics of the topic: The most advanced modern designs are combined crowns, consisting of a cast metal frame and a facing layer of porcelain, polymer or light-curing composite material. Aesthetic plastic crowns are also widely used in prosthetics, so mastering the technique of preparing teeth for these types of crowns is mandatory for an orthopedic surgeon. Independent preparation of teeth for crowns contributes to the formation of the necessary manual skills and abilities.

The purpose of training: Master the technique of preparing teeth for combined and plastic crowns, and the technique of creating ledges. To study the clinical and laboratory stages of manufacturing combined and plastic crowns.

Specific Goals

Practical lesson plan

Self-training work plan

1. Write down in a notebook the features of preparing various groups of teeth for a cast combined crown. Requirements for a properly prepared tooth.

2. Draw up an algorithm for the clinical and laboratory stages of manufacturing cast combined crowns.

3. Sketch the types and shapes of ledges created when preparing a tooth for a combined crown.

4. Write down in a notebook the specifics of preparing various groups of teeth for a plastic crown. Requirements for a properly prepared tooth.

5. Draw up an algorithm for the clinical and laboratory stages of manufacturing a plastic crown.